Coating knowledge: the latest research progress of nano semiconductor thermal insulation coating

Core tip: nano semiconductor powder plays an important role in thermal insulation of nano semiconductor coating The barrier effect of coating on thermal radiation is the result of absorption and reflection The proportion of absorption and reflection will be different due to the different properties of semiconductor materials In addition, the particle size of materials is related to its performance For a single nano particle, the larger the particle size is, The larger the cross-section is, the larger the area that nano particles can block sunlight through absorption and reflection However, for the coating as a whole, the larger the total block area (a) of nano semiconductor powder is, the better the thermal insulation effect in theory A can be used to represent the nano semiconductor thermal insulation coating Paint knowledge | precautions for wall paint color selection Recommended introduction: when painting the wall, the owner sometimes has difficulty in choosing what color of the wall paint to paint In fact, there is no ugly color in the wall paint, only the disharmonious color matching The use of wall color contains the knowledge of health Too strong color will stimulate people's perception, make people have a sense of fidgety, affect people's mental health Grasp the basic principles of wall color and paint a colorful space 1、 Wall paint color selection notice 1 Light color is generally used for the top surface Light colors make people feel light, dark colors make people feel heavy Usually, the treatment of rooms is from top to bottom, from shallow to deep For example, the ceiling and walls of rooms are white and Home of coatings: nano semiconductor powder plays an important role in thermal insulation of nano semiconductor coatings The barrier effect of coating on thermal radiation is the result of absorption and reflection The proportion of absorption and reflection will be different due to the difference of the properties of semiconductor materials In addition, the particle size of materials is related to their performance For a single nano particle, the larger the particle size and the larger the cross-section, the larger the area that nano particles can block sunlight through absorption and reflection But for the coating as a whole, the larger the total cross-sectional area (a) of the internal nano semiconductor powder, the better the thermal insulation effect in theory A can be expressed in formula (1) The latest research progress of nano semiconductor thermal insulation coating In the formula: a - Total breaking area, cm2; m - total mass of nano powder, G; R - particle size, cm; ρ - density, g / cm3 It can be seen from formula (1) that the smaller the particle size of nano semiconductor is, the larger the total cross-sectional area is However, when the particle size is too small, the change of the electron density of the particle will reduce its shielding function to sunlight, so the nano semiconductor particles prepared need to have appropriate particle size It can be seen from the above analysis that the thermal insulation effect of nano semiconductor particles is the result of the interaction of physical structure of semiconductor itself and particle size Among many nano semiconductor particles, nano indium tin oxide (ITO) and tin antimony oxide (ATO) are the first metal oxides used in nano thermal insulation coating The carrier concentration of ITO and ATO film is 1020 pieces / cm3, the visible light transmittance is 80% - 90%, and the infrared reflectivity is 75% - 80% The infrared emissivity will increase with the increase of carrier concentration According to the optical test of ITO nano thermal insulation coating by Huang Xushan, the infrared barrier of ITO nano thermal insulation coating is mainly concentrated in the band of 1200-1500nm, and the infrared barrier in this area can reach 95% The thermal insulation test shows that when the content of ITO nano particles reaches 1.5% of the coating quality, the thermal insulation effect of the coating is the best, and the thermal insulation effect of the coating is 5min under the irradiation of infrared lamp The comparison shows that the temperature of the glass coated with nano thermal insulation coating is about 40 ℃ lower than that of the blank glass Sun Guoliang and others found that there are two states of sb in the coating, Sb3 + and sb5 + When the Sb content is low, sb5 + is dominant, and the carrier number is small, and the infrared barrier rate is low; With the increase of Sb content, the number of carriers increases, and the infrared barrier rate increases; when Sb content reaches 6%, the infrared barrier rate is the highest, and when it exceeds 6%, the infrared barrier rate decreases There are two main reasons for this: first, the lattice distortion of SnO2 caused by high Sb content, the electron dispersion becomes larger, and the mobility of carriers is reduced; Second, due to the increase of sb, Sb3 + is gradually increasing, and Sb3 + is like an electronic trap, which eliminates the electrons generated by sb5 + and reduces the carrier concentration, so the infrared barrier rate is also reduced In addition, Mei et al Studied the content of ATO in ATO / epoxy resin thermal insulation coating, the results show that with the increase of ATO content, the thermal insulation effect is increased, and the optimal content of ATO is 2% of the total coating mass In recent years, with the continuous development of new materials, people have been looking for new nano particles to replace the original ITO and ATO Li et al Tried to add nano ZnO doped with Al into the thermal insulation coating, and ZnO itself is a semiconductor material The ZnO carrier concentration added with Al increased significantly, and the conductivity and infrared barrier also increased The research shows that the thermal insulation coating with 0.5% ZnO (in which the mole fraction of Al is 6%) has the best infrared barrier, reaching more than 80% Zhao et al Mixed gallium (GA) into ZnO to make GZO film The results show that when the content of GA is 4.9%, the infrared light reflectivity of the film can reach 70%, and the transmittance is less than 1% At this time, the visible light transmittance is still above 90% The visible GZO coating is an ideal insulating coating for glass In addition to ZnO dopants, Chen Zhonghua and others added nano zirconia into the thermal insulation coating, and studied the microstructure of the coating The results showed that the coating had a good barrier effect on infrared ray, nano particles filled the gap between the coating tightly, forming a complete air thermal insulation layer, greatly improving the thermal insulation performance of the coating Wang et al Mixed the rare earth element yttrium with antimony oxide to prepare yttrium antimony oxide nano meter powder, and then prepared yttrium antimony oxide nano thermal insulation coating Optical detection shows that the reflectivity of this coating is more than 90% in the range of 450-1600nm, more than 80% in the range of 1600-2200nm, higher than that of ZnO and ITO films The application of nano semiconductor powder has greatly changed the heat insulation mechanism of thermal insulation coating, but the specific surface area of nano powder is large The surface energy is high and the nanoparticles are easily generated by interfacial interaction Therefore, the dispersion of nanoparticles in coatings is always one of the difficulties in coatings research To promote the marketization of semiconductor nano insulation coatings, we must strengthen the research on nanoparticle dispersion system [focus on WeChat official account "coating network"; 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